Test for valid hyperlink to a file

[JFistere]

I calculate a series of hyperlinks in a column, only some of which refer to actual files on my computer (not on the Internet). I would like to test for the existence of the file and use the result in an if statement, and display the link if it exists, or leave the cell displaying blank if it does not.

It is not feasible to continuously test for the existance of a file, of course, so perhaps it should test on opening the spreadsheet or when F9 is pressed.